Method and apparatus for underwater irradiation of substances



1968 F. M. BLACHE-FRASER ETAL 3,417,239

METHOD AND APPARATUS FOR UNDERWATER IRRADIATION OF SUBSTANCES Filed May 7, 1965 2 Sheets-Sheet l 1968 F. M. BLACHE-FRASER ETA!- 3,417,239

METHOD AND APPARATUS FOR UNDERWATER IRRADIATION OF SUBSTANCES Filed May 7, 1965 2 Sheets-Sheet z FIG-3 United States Patent 3,417,239 METHOD AND APPARATUS FOR UNDERWATER IRRADIATION OF SUBSTANCES Francis M. Blache-Fraser, David R. Cowper, and Eric K. Curnow, Ottawa, Ontario, Canada, assignors to Atomic Energy of Canada Limited, Ottawa, Ontario, Canada, a company Filed May 7, 1965, Ser. No. 454,149 Claims priority, application Canada, Mar. 5, 1965, 924,809 17 Claims. (Cl. 25052) ABSTRACT OF THE DISCLOSURE Method and apparatus for the irradiation of substances wherein the substances are placed on a platform with a hole in it, and an air bubble surrounds the platform. The assembly of air bubble, platform and substances thereon are lowered into a pool of water which contains a radioactive source. In the operative position, the radioactive source reaches through the hole in the platform into the air bubble to irradiate the substances.

This invention relates to a method and apparatus for underwater radioactive irradiation of substances.

The use of water as a biological shielding is well recognized. Where water has been disposed in containers around sources or irradiation areas the necessary volume of water to give adequate protection has monopolised floor space and made more complicated the movement of the substances to be irradiated and/or the radioactive source. Deep tanks or pools in the floor have proved attractive from the point of view of saving floor space when storing capsules of radioactive material. The present invention contemplates not only the submersion of sources for shielding purposes, but the submersion of substances to be irradiated into close proximity to such submerged sources. In order to simplify the irradiation of batches of substances the present invention provides novel displacement techniques and apparatus, of comparative simplicity. Since the source is fixed andshielded by the water in the pool, the building COSiQztQrhOllSG such a facility is low in comparison to those facilities where the source is raised from the pool necessitating additional costly shielding and source shielding.

It is an object of one aspect of the invention to provide a method for underwater radioactive irradiation of substances.

In accordance with the foregoing aspect of the invention there is provided the steps of: floating said substances on the surface of said liquid; disposing a source of radioactive radiation under the surface of said liquid; enclosing a volume of gas in the vicinity of said substances, above the surface of said liquid; and, sinking said substances and said volume of gas until said substances are adjacent said source and irradiated thereby, said volume of gas preventing liquid from rising to said substances.

It is an object of another aspect of the invention to provide apparatus for the underwater irradiation of substances.

In accordance with this other aspect of the invention, the apparatus comprises: a liquid biological shielding pool; a source of radioactivity at the bottom of said pool; a float for receiving said substances; a bell having an opening at the bottom thereof, said bell being adapted to selectively enclose said float and substances, said bell entrapping gas within itself when submerged in a liquid; and, means to lower said float, substances, and bell as an entity into said pool for bringing said substances into proximity to said source, said entrapped gas preventing said liquid from contacting said substances.

Patented Dec. 17, 1968 A preferred embodiment of the invention will now be described with reference to the accompanying drawings in which:

FIG. 1 shows a water tank with a submerged source, a batch of substances to be irradiated and a cover, the latter two being shown prior to immersion.

FIG. 2 is similar to FIG. 1 but with the batches and cover submerged.

FIG. 3 shows details of a lock suitable to joining together parts of the assembly shown in FIG. 1.

Referring now to FIG. 1 the apparatus generally comprises a pool 1, a floating assembly 2, a stand 3, a bell 4 and a source assembly 5.

The pool 1 has a bottom 11, sides 12 and ends 13, and contains water having a surface level 14.

The pool 1 must be of sufiicient depth to accommodate the floating assembly 2 and the bell 4 and having linear dimensions to afford adequate biological shielding to any personnel working above the level of the surface 14.

Projecting upwardly from the bottom 11 of the pool 1 and rigidly aflixed thereto is a source stand 51 for supporting the source 5. The source 5 may comprise a plurality of tubes 52, disposed around a common pitch circle, and each containing a radioactive source, for example, Co The source 5 may be lifted off the stand 51 by remote handling means.

Upon the surface 14 of the water there is shown a floating assembly 2 comprising a buoyancy tank 21 having an upstanding central cylinder guide 22 open at the bottom and aflixed to the tank 21 by a water-tight joint. The cylinder guide 22 is adapted to be slidably received over the source 5 as will be described. Spaced around the tank 21 are a number of inner guide channels 23 which serve to support a top plate 24. The channels 23 may be extended below the tank 21 in order to form feet 23a. The tank 21 has on its top surface a number of lower bearings, not shown, which are axially aligned with a corresponding number of apertures 25 inthe top plate 24 spaced around a common pitch circle. Extending between the lower hearings on the tank 21 and the apertures 25 in the plate 24 are a number of spindles 27 adapted for rotation and each spindle having sprocket wheels 28. The sprocket wheels 28 are interconnected by a chain 29 which is driven by a further sprocket (not shown) on motor 26.

The motor 26 may conveniently be an air motor, the exhaust of which will pressurize the bell 4. Otherwise the motor may be an electric motor and a separate air supply 47 is required to replace the trapped air which will become moisturized and ozonized. This stale air will escape from around the rim 43 of the bell. Should the bubbles thus produced prove a nuisance, a separate discharge pipe may be provided a suitable throttle device incorporated into the discharge pipe, if necessary, to control the pressure within the bell.

Each spindle 27 carries a top plate 30 and a bottom plate 31 and the two plates are separated by four longeron members 32 forming cages 33 inside of which batched substances 34 may be stowed.

The hell 4 has a top 41 sides 42 and a weighted rim 43, and above its rim 43 is airtight. A lifting eye 44 is provided at the top. On the inside of the sides 42 are vertically disposed a number of outer guide channels 45 adapted, in operation, to receive the inner guide channels 23 on the floating assembly 2, as will be described. Four eyelets 46 project radially outwardly from the sides 42 and are disposed on a common diametral plane. The eyelets 46 co-operate with guide lines to be described.

Referring now to FIG. 3 there is shown a locking device 6 several of which may be spaced around the periphery of the bell 4 adjacent the rim 43 thereof. FIG. 3 shows a portion of buoyancy tank 21 and one of the inner guide channels 23 attached thereto. A portion of the 3 bell 4, with its weighted rim 43, is shown at 42 in juxtaposition with one of the inner guide channels 23. The locking device 6 comprises a block 61 having a channel-shaped cross-section with arms 62 and 64 having apertures 65 and 66 respectively therein, the aperture 66 being slightly smaller in diameter than that of aperture 65. The block 6 is welded to the bell 4 as at 67, the bell having a clearance hole 68 therein co-axially disposed to apertures 65 and 66. Inner guide rail 23 on the floating assembly 2 also includes an aperture 69. A bolt 70 is slidably received in apertures 65 and 66 and has two diameters forming at shoulder 71 against which abuts one end of a compression spring 72, the other of which abuts against arm 64 of the block 61. The bolt 70 includes a transverse aperture at 73 for receiving a removable stop pin 74 slidably received in an aperture 75 in the block 61.

The stand 3 includes upright members 301 and a horizontal top member 302 to which is slung a monorail 306 on which runs a hoist 303 having a cable 304 and hook 305. A pair of taut guide lines 48 are firmly attached to the bottom 11 of the pool 1 and the top member 302 and the eyelets 46 on the bell 4 co-operate with the guidelines 48 to steady the assembly during raising and lowering.

In operation, batch substances 34 for irradiation are stowed in the cages 33 as the tank assembly 21 floats on the surface of the pool 1. The bell 4 is then lowered by the hoist 303 onto the tank assembly 21 by sliding the outer guide channels 45 on the bell 4 over the inner guide channels 23 on the tank assembly 21 until the entire floating assembly is received within the bell 4. Further and gradual lowering of the bell 4, assisted by the weighted rim 43, brings the source into the interior of the cylinder guide 22 and eventually the feet 23a rest on the bottom 11 of the pool 1. Since the bell 4 is airtight substantially no water will flow into the bell, at least, no water will come close to the batched substance 34. Once the lowering operation is completed, as shown in FIG. 2, the air motor 26 or the electric motor provided to rotate the batched substance will be energized and the irradiation of the latter will occur. Rotation of the cages 33 ensures substantially even irradiation of the substance.

If it be desired to raise both the bell 4 and the floating assembly 2 out of the water the bolts 70 of the locking devices 6 may be moved radially inward to engage the inner guide channels 23. The bolts 70 are then locked in this position by the stop bolts 74. The whole equipment may then be lifted bodily out of the water.

The locking device 6 may be utilized so that in the event of the water level Within the submerged bell rising beyond a selected level the hoist will automatically raise the entire assembly out of the Water.

While there has been shown and described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined by the appended claims.

We claim:

1. Apparatus for the underwater irradiation of substances comprising:

(i) a liquid biological shielding pool,

(ii) a source of radioactivity at the bottom of said pool,

(iii) a float for receiving said substances,

(iv) a bell having an opening at the bottom thereof, said bell being adapted to selectively enclose said float and substances, said bell entrapping gas within itself when submerged in liquid, and,

(v) means to lower said float, substances, and bell as an entity into said pool for bringing said substances into radioactive proximity to said source, said entrapped gas preventing said liquid from contacting said substances.

2. Apparatus for underwater irradiation of substances comprising:

(i) a liquid biological shielding pool,

(ii) a source of radioactivity extending upwardly from the bottom of said pool,

(iii) a float for receiving said substance, said float 'having an aperture therein for selectively receiving said source,

(iv) a bell having an opening at the bottom thereof, said bell being adapted to selectively enclose said float and substance, said bell entrapping gas within itself when submerged in liquid, and,

(v) means to lower said float, substance and bell as an entity into said pool for bringing said substance into radioactive proximity to said source, said entrapped gas preventing said liquid from contacting said substance.

3. Apparatus as defined in claim 1 including cages for receiving said substance, and means for rotating said cages, relative to said source, when said entity is submerged, for ensuring substantially uniform irradiation of said substances.

4. Apparatus as defined in claim 2 including cages for receiving said substances, and means for rotating said cages, relative to said source, when said entity is submerged, for ensuring substantially uniform irradiation of said substances.

5. Apparatus as defined in claim 1 including means for introducing fresh gas into said bell thereby to reduce the moisture content and ozone level therein.

6. Apparatus as defined in claim 2 including means for introducing fresh gas into said bell thereby to reduce the moisture content and ozone level therein.

7. Apparatus as defined in claim 1, including locking means for selectively mechanically joining said float and hell.

8. Apparatus as defined in claim 7, including locking means for selectively mechanically joining said float and bell.

9. Apparatus for the underwater irradiation of substances comprising:

(i) a liquid biological shielding pool,

(ii) a source of radioactivity in said pool,

(iii) a platform for supporting substances to be irradiated, said platform having an aperture therein for receiving said source,

(iv) a means for trapping a volume of gas said means being adapted to enclose said platform .and the substances supported thereon, and

(v) means for depressing said platform, substances, and said gas trapping means into the pool so as to bring said substances into radioactive proximity to said source in a gas environment.

10. Apparatus as defined in claim 9, including means for rotating the substances supported on said platform for insuring uniform irradiation of said substances.

11. Apparatus as defined in claim 9, including means for introducing fresh gas into said gas trapping means.

12. Apparatus as defined in claim 9, including locking means for selectively mechanically joining said gas trapping means and said platform.

13. Apparatus for the underwater irradiation of substances comprising:

(i) a liquid biological shielding pool,

(ii) a source of radioactivity in said pool,

(iii) a platform for supporting substances to be irradiated, said platform having an aperture therein for receiving said source,

(iv) a tubular member adapted to enclose said platform and the substances supported thereon,

(v) a top closure means for said tubular member and cooperating therewith to cause a volume of gas to be trapped above said platform, and

(vi) means for depressing said platform, substances, said tubular member and said top closure into the pool for bringing said substances into radioactive proximity to said source in a gas environment.

14. An apparatus as claimed in claim 13 in which said tubular member and said top closure are integral.

15. Apparatus as defined in claim 13, including means for rotating the substances supported on said platform for insuring substantially uniform irradiation of said substances.

16. Apparatus as defined in claim 13, including means for introducing fresh gas into said tubular member.

17. Apparatus as defined in claim 14, including locking means for selectively mechanically joining said tubular member and said platform.

US. Cl. X.R. 250106 

